Refrigerating system



April 26, 1932. J. DuBRovlN 4REFRIcnszRMIING SYSTEM Filed` Feb. 23, 19283 Sheets-Sheet April 26, 1932. J. DuBRovlN REFRIGERATING SYSTEM FiledFeb. 23, 1928 3 Sheets-Sheet 2 (f5/717 DuraV/'f 5% Y /Z April 26, 1932J. DUBRoviN 1,855,754

REFRIGERATING SYSTEM Filed Feb. 2s, 192s s sheets-sheet s I j' Y 4f l 43f f 7 .loy l' WM Y l l; 'A ity! Patented Apr. 26, 1932 PATENT OFFICEJOHN DUBRDVIN, F LOGAN SPORT, INDIANA REFRIGEBATING SYSTEM Applicationfiled February23, 1928. Serial No. 258,303.

My invention relates to compression refrigerating systems and in some ofits general objects aims to improve the efiiciency of the entire system,to reduce the sizes of the condenser and motor required for a givenrefrigerating capacity, to reduce the required amount of refrigerant, toeliminate the need of an oil separator, to insure a sensitivetemperature control, and to avoid expansion valve troubles.

Compression refrigerating systems employing refrigerants of the generalclass of sulphur dioxide, ethyl chloride and the like, usually havepiping through which the refrigerant passes successively from thecompressor through the condenser, the expansion valve (and sometimesthrough a receiver between the condenser and the expansion valve),through an eyaporator, and then back to the compressor. Such systemscommonly have the following objections, which my invention particularlyaims to overcome:

(l) In operating such a system in refrigerators designed for households,from onethird to one-half of the total refrigerant usually remains inthe condenser during the pe- I riods when the compressor is not running.

Consequently. the condenser must have a correspondingly large liquidstorage capacity, or must be supplemented by a liquid-storing receiver,and a correspondingly large amount of refrigerant must be provided. Vhenthe compressor again starts ruiming, a heavy motor torque is needed tostart against the high pressure due to the presence of liquid in thecomparatively Warm condenser, thus requiring a larger size of motor thanwould other- Wise be ample. My invention aims to overcome theseobjections by providing a refrigerating system in which the condenser issubstantially emptied during each period in which the compressor is notrunning, and by reducing the pressure of the condenser during each suchidle period, thereby greatly reducing the needed size of condenser andlikewise reducing the starting torque of the compressor.

(2) The lubricating oil Which accumulates in the condenser along withthe liquid refrigerant during the Working of the compressor,

also occupies considerable space in the condenser, thus furtherincreasing the needed size of the condenser. And, since this oil is apoor conductor of heat, its presence greatly reduces the eiiciency ofthe condenser. While the last mentioned difficulties may be reduced byemploying an oilseparator, this in turn involves an increased initialcost, together with the diculty of keeping the needed oil-return valveadjusted and free from clogging. My invention aims to overcome theseobjections by providing a system in which oil as Well as liquidrefrigerant will continually trickle or seep from the condenser to theevaporator While the compressor is running, so that no large amount ofoil will accumulate in the condenser, thereby further reducing therequired size of the condenser and greatly increasing the eiiiciency ofthe condenser.

(8) Compression refrigerating systems also commonly employ an expansionvalve of a needle valve type, which is ditiicult to maintain in properadjustment and apt to clog, and which varies greatly in effectivenessWith its wear, thereby impairing the eiciency of the system and oftencausing a chattering ofthe valve. My invention aims to overcome thesediificulties by providing a valve which never closes entirely and henceeliminates the likelihood of clogging, which requires no close tting tipadapted to Wear unduly, and which will require no adjusting.Furthermore, my inventionprovides a system in Which the valve affords anunusually large passage when opened, so that the liquid refrigerant canquickly iiush oii'` any particles of impurities adhering to thecondenser piping, the valve portions, or other interior parts.

(4) In the usual compression refrigerating systems, a bursting (orexplosion) of the condenser piping sometimes occurs, owing to anexcessive increase of pressure in the condenser in case the systembecomes deranged. My invention aims to overcome this by providing avalv'e arrangement which will automatically relieve such an excessivepressure in the condenser by freely connecting the condenser to theevaporator.

Furthermore, my invention provides simple means for simultaneously andpositively moving the liquid control valve to its liquidthrottlingdisposition when the compressor is started, and for keeping it sodisposed 'until the pressures in the evaporator is substantially reducedand the compressor is halted. Then the throttling of liquid by the valveis greatly increased and the pressures in the system are substantiallyequalized so as to reduce the back pressure against which the compressormust be started in the usual compression type refrigerating systems. Myinvention also provides a system in which the entire control means areeasily manufactured, durable and not likely to get out of order, and onein which neither a spring nor a diaphragm will be required in the liquidcontrol valve.

Still further and also more detailed objects will appear from thefollowing specification and from the accompanying drawings, in which ig.1 is asomewhat diagrammatic view of a compression system embodying myinvention and including a liquid control valve magnetically actuated inone direction, with the compressor shown in central and verticalsection.

Fig. 2 is an enlarged central and longitudinal section through theliquid control valve of Fig. 1, showing the plunger in the throttlingdisposition in which it is electromagnetically retained as long as thecompressor is running.

Fig. 3 is a central and vertical section through lower end portions ofthe same valve, showing the position of the lower end of the plungerwhen the plunger hasbeen lifted by the pressure of liquid .refrigerantafter the compressor was halted.

Fig. 4 is a horizontal section taken along the line 4-4 of Fig. 3,showing the slots in the plunger which afford liquid passages.

Flg. 5 is a partially sectioned enlargement of the current-controllingvalve of Fig. 1.

Fig. 6 is a diagrammatic view of another compression system embodying myinvention, namely one in which a single diaphragm-actuated valve stemactuates an electric switch for controlling the motor-driven compressor,and also mechanically governs the liquid 'control valve.

Fig. 7 is an enlarged central and vertical section through the valve ofFig. 6.

Fig. 8 is a horizontal section taken along the line 8 8 of Fig. 7.

Fig. 9 is a diagrammatic view of another embodiment of my invention,namely one in which the liquid-control valve is mechanically responsiveto the starting and stopping of the compressor.

Fig. 10-is an enlarged central and vertical section through the liquidcontrol valve of Fig. 9.

Fig.k 11 is an enlarged side elevation of the tip of the liquid controlvalve member of Fig. 7.

Fig. 12 is a partially sectioned enlargement of the medial portion ofthe movable valve member of the valve of Fig. 10.

Referring first to the embodiment of Figs. 1 to 5 inclusive, Fig. 1shows a compressor including a piston 1 connected by a pitman 2 and acrank 3 to the shaft 4 of an electric motor 5.

An intake pipe 6 leads to the crank casing 7 of the compressor, while anoutlet pipe 8 connects the compression chamber 9 of the compressor withthe condenser 10. The discharge end of the condenser is connected to thetop of the evaporator 11 through a liquid control valve and a connectingpipe 12, and the intake pipe 6 leads from this evaporator to thecompressor to complete the circuit for the refrigerant.

The liquid control valve includes a tubular and desirably upright shell13 spaced radially from a plunger-guiding tube 14 by portions of a lowerhead 15 and an upper head 16, and a solenoid coil of wire 17 is disposedin the annular space between the said tube and shell. The valve bottom15 has a threaded inlet 15B to which the discharge end of the condenser10 is connected and has its vertical bore reduced in diameter at itsupper end, desirably by inserting a bushing 18 (Fig. 3) having arelatively minute bore, and the upper end of this nipple is above thebottom of the solenoid coil 17. The upper end of the guide tube 14carries a nipple 19 for connecting it to the pipe 12 which leads to theevaporator, and this nipple has its lower end spaced from the top of thevalve bottom by a distance considerably greater than the length of asoft iron plunger 2O which is freely slidable in the guide tube 14. Thisplunger 20 desirably has longitudinal slots 21 extending radially inwardfrom its periphery and also has a bottom recess 22 opening into theseslots 21, while the lower end of the nipple 19 has transverse slots 23which will connect the slots 21 with the bore of the nipple 19 when theplunger is raised so that its upper end abut-s against the bottom of thenipple.

The solenoid 17 is connected to the motor circuit 24 and to anoscillating mercury switch 25 which simultaneously controls the flow ofcurrent to both the motor and the solenoid of the liquid control valve,for which purpose the solenoid is here shown as connected in series withthe motor 5. although the arrangement of the circuit connections is notmaterial. The switch 25 is pivoted on a riser 26 mounted on the cover 27of a diaphragm casing 28, through a lever 29 which has an approximatelyhorizontal arm provided with an approximately vertical slot 30.Extending downwardly into the casing 28 through the cover 27 is a thruststem 31 carrying at its upper end a transverse pin 32 which moves in theslot 30, while the lower end of the thrust stem 31 carries a disk 33.Connecting this disk 33 with the cover 27 is a bellows-like tubularmember 34 of sufficient flexibility to be expanded or contracted inlength by differences in pressure between the interior and exterior ofthis member, which bellows member is sealed at its ends respectively tothe disk 33 and the cover 27. A compression spring 35 within the saidbellows member is interposed between the disk 33 and the bottom of anipple 36 through which the thrust stem 31 loosely extends, and thisnipple is threadedly connected tol the cover 27 to permit an adjustingof the pressure of the spring. A pressure pipe 37 leads from the top ofthe evaporator 11 to the bottom of the casing 28, so that the interiorportion of the casing surrounding the bellows member 35 and below thedisk 33 is at the vapor pressure in the evaporator, while the interiorof the bellows member is subjected to the pressure of the outer air. Themovement permitted to the stem pin 32 by the length of the slot 30 inthe lever which carries the mercury switch afs fords lost motion topermit a quick snapping action of the switch in response-tocorresponding pressure increases or decreases in the evaporator, so thatthe mechanism as just described simultaneously controls the How ofcurrent to the motor and to the solenoid of the liquid control valve, inresponse to the pressure variations within the evaporator for which thespring 35 was adjusted by the setting of the nipple 36.

With my refrigerating system thus arranged. current is only supplied tothe solenoid 17 while the compressor isoperating, thus holding theplunger during the operation of the compressor in the position shown inFig. 2, in which portion liquid refrigerant can only seep slowly throughpassages restricted in size by the diameter of the valve bottom bore18.Thus disposed, the throttling position of the plunger permits bothliquid refrigerant and oil to pass continuously but at a slow rate fromthe"condenscr to the evaporator, as the action of the solenoid holds theplunger in its said position against the pressure due to the operationof the co1npressor, and the pressure in the condenser and the evaporatortend to equalize while the compressor is running. This continuous flowthrough lthe valve avoids the accumulation of both liquefied refrigerantand oil 'in the condenser, and continues until the suction of thecompressor through the intake pipe fi has reduced the vapor pressure inthe condenser below that for which the spring 35 associated with theswitch was adjusted.

lVhen this critical minimum pressure is reached, the spring snaps theswitch to its below it, presses liquid refrigerant and oil (if present)up through the bottom bore 18 of the liquid control valve and againstthe bottom of the plunger, thereby forcing the plunger up against thestop nipple 19 in the top of the casing of this valve. This effectivelyopens the valve to a greater extent and permits a more rapid flow of theliquid refrigerant into the evaporator, so that the latter will house byfar the greater part of the refrigerant by the time the vapor pressurein the upper portion of the condenser is substantially equal to that inthe evaporator. The approach to pressure equalization may vary somewhatwith the weight of the plunger and with the arrangement of the pipesleading to and from the casing of the liquid valve, but such variationsare relatively immaterial.

When this pressure equalization is reached, the plunger gradually sinksto its downward or liquid-throttling position and gravity holds it therewhile the withdrawal of heat from the evaporator as for example by thefood chamber in which the evaporator is disposed) has raised the vaporpressure in the evaporator to the point where the bellows member 34 issufficiently collapsed to move the switch back to its on position ofFigs. 1 and 3. The closing of the circuit through the motor then startsthev compressor again, while the simultaneous closing of the circuitthrough the solenoid causes the latter to exert its downward pull on theplunger 2O of the liquid control valve. Since this plunger had alreadydropped by gravity upon the valve bottom before this occurs` there canbe no chattering. The suction of the compressor then again drawsrefrigerant vapor out of the vaporizer, while the pressure of freshlycompressed vapor fed to the condenser slowly forced more liquefiedrefrigerant through the valve into the evaporator.

Owing to the relatively wide opening of the valve when the plunger wasraised and to the above described previous equalizing of pressure.relatively little liquid refrigerant (or none at all) was left in thecondenser when the compressor is again started. and the pressure ofvapor in the compression chamber of the compressor and in the upperportion of the condenser had also been greatly reduced during the idleperiod of the compressor, as this vapor expanded while forcing liquidrefrigerant out of the condenser into the evaporator. Consequently, theinitial strokes of the compressor encounter very little back pressure,thus reducing the starting torque required in the motor and therebypermitting the use of a lower poweredmotor for a given size ofcompressor. So also, the relatively small amount of warmed liquid whichwas left in the condenser produces only a rather negligible effect onthe evaporator when forced into the latter.

When my refrigerator is thus operating, the condenser is cleared oflubricant during each idle period of the compressor, and the absence ofthe usually large amount of oil in the condenser greatly increases theheat trans- Lfer through the condenser, thereby increaslng theefficiency of the latter. By deliberately permitting seepage from thecondenser to the evaporator through the valve while the compressor isrunning, I avoid the need of a needle valve member, or other tightlyseating movable valve member, and can employ an unusually durable valvearrangement in which a hard and acid-proof material may be used both forthe valve seat and the plunge1' bottom. Since both the valve seat andthe valve bore are amply flushed whenever the plunger 1s ralsed, anyparticles of impuritles are then washed away, thereby preventing.

all clogging and insuring the desired seepage flow. Since the radialslots 21 in the plunger also deter eddy currents, my electromagneticallyoperating valve can readily be used on alternating current as well asdirect current circuits, and particularly so, since this valve iscontinuously cooled by the refrigerant which passes around the solenoidcore (plunger) and through the slots in the latter.

The pressure-controlled switch also can be of a quite simple and ruggedconstruction,

y as shown for example in Fig. 5 and with the major portion of therefrigerant housed by the evaporator, the desired approximate uniformityof the temperature around the evaporator can be obtained with theoppositely directed movements of the switch-actuating stem 31 responsiveto considerable differl ences of the vapor pressure in the evaporator.

Consequently, no highly delicate adjustment or readjustment of thespring-pressure regulating nipple 36 is required, which is the onlyadjustable portion of the entire refrigerating system shown in Fig. 1.To prevent liquid refrigerant from entering the pipes 6 and 37, theseshould lead to the vapor space at the top of the evaporator, but thearrangement shown diagrammatically in Fig. 1 may otherwise be modifiedin many ways.

Moreover, while I have heretofore described my refrigerating system asincluding an electromagnetic valve, I do not wish to be limited in thisrespect, as other liquid control valves may be employed to goodadvantage if also operated in substantial unison with the starting andthe stopping of the compressor.

For example, Fig. 6 shows another embodiment of my invention, in whichthe switchactuating stem 41 extends downward into a valve casing 42through which the liquid refrigerant iows from the condenser 10 througha pipe 37 intb the evaporator 11. In this case, a generally horizontaldiaphragm 43 has its edge portion clamped between the mouth of the valvecasing 42 and the cover 44. The

valve stern 41 extends vertically through the center of the diaphragmand is sealed to the latter (as by soldering), and the lower` positionof the stern extends through one arm 45 of a bell-crank lever which isheld in pivoting engagement with a notched bracket 46 (mounted in thecasing) by a spring 50. The other lever arm 47 carries a valve tip 48shaped so that it can throttle the inlet to the casing from the pipe 10,and the stem has enlargements 51 and 52 disposed respectively forengaging upper and lower faces of the lever arm 45 but spaced to permitlost motion so that the diaphragm 43 can flex from its upwardly boweddisposition of Fig. 7 to the downwardly bowed form shown in dottedlines.

When moved to the latter position by the snapping of the spring 50, thebottom of the enlargement 52 is still above the bottom of the casing, soas to allow the flow of liquid into the pipe 37; and in the same (dottedline) position the lever tip 41 is freely spaced from the adjacent wallof the casing to permit liquid to enter from the pipe 10. lVhen thelever is in its raised (full line) position of Fig. 7, the lever tip 48seats in the inlet from the pipe 10, the entrance of the liquid is thenthrottled, as it can only iow through a suitable passage provided atthis tip, such asthe slot 54 of Fig. 11. Thus arranged, a rise of vaporpressure in the evaporator 11 to a point suflicient for snapping thediaphragm 43 upwardly will raise the diaphragm, thereby causing thevalve-tip 41 of the lever to throttle the flow of liquid from thecondenser through the valve casing to the evaporator, while the samemovement of the diaphragm rocks the switch 25 to its on position andstarts the driving of the compressor. Likewise, a drop of pressure inthe evaporator (and hence in the casing 42), to the point where thepressure of the outer air will flex the diaphragm downwardly, will rockthe lever to the dotted position of Fig. 7. This movementhalts thecompressor and permits the free How of liquid refrigerant from thecondenser to the evaporator to flush the condenser and the valve casing,also permitting a substantial emptying of the condenser and anequalizing of the pressures in the condenser and evaporator.

Fig. 9 shows still another embodiment of my invention, namely one inwhich the switch 25 is actuated in response to the vapor pressure in theevaporator, after the manner of the switches in Figs. 1 and 6, but theswitch is electrically connected only to the electric motor 5, so as tostart and stop the latter in response to vapor pressure variations inthe evaporator. The crank-shaft 4 of the compressor has a bushing 55fastened to it by a set screw 56, while another bushing 57 is slidablysupported on the shaft and extends beyond the end of the shaft, as shownin Fig. 10. This slidable bushing 57 has a projecting stem 58 disposedfor exerting an inward thrust on the bottom 59 of a bellows member 60which has its other end sealed to the perforated cover 61 of astationary casing 62, which casing is supported (by means not shown inthe drawings) for alining the casing axially with the shaft. A ball 63is preferably interposed between the tip of the stem 58 and the bottom59 of the bellows member to reduce friction between these parts. Thebottom of the casing 62 has an outwardly extending tube 64 through whichthe interior of the casing is connected to the condenser 10, and thisconnection is controlled by a. valve member 65 which engages the bottom59 of the bellows member, and which valve member is continually pressedagainst the said bottom by a spring 66, and the interior of the casingis also connected to the evaporator 11, as shown in Fig. 9. The shaftbushings 55 and 57 are connected by normally straight and resilientmembers 88, each of which carries aweight 59.

When the compressor is not running, these resilient members 88 hold theslidable bushing 57 in the osition shown in full lines in Fig. 10, therey forcing the bottom of the bellows member, together with the valvemember 65 away from the end of the shaft 4 and holding the closureportion of the valve away from a seat 67 in the tube 64, therebyaffording a full open connection from the' condenser to the evaporator.As soon as compressor starts running, the rotation of the shaft 4 and ofthe resilient members 58 causes the Weights 59 to separate bycentrifugal action, thereby flexing these members 88 outwardly anddrawing the slidable bushing 57 away from the valve and diaphragm casing62. This permits the spring 66 to seat the valve member 65, but slots 68in the head of this valve member (shown in Fig. 12) still maintain athrottled connection to permit a seepage of liquid refrigerant and oilfrom the condenser to the evaporator.

In each of the illustrated embodiments, the starting and stopping of thecompressor is responsive to differences in the vapor pressure within theevaporator, and the liquid control valve is held in a position as longas the compressor is running but is released and moved to a full openposition when the cornpressor is halted. Consequently, neither liquidrefrigerant or oil can accumulate to any considerable extent in thecondenser, and by far the greater part of the refrigerant iscontinuously stored in the evaporator. Since the connection between thecondenser and the evaporator is never entirely shut of, no perfectfitting of the valve parts is required (as in the expansion valves nowcommonly employed) and the wear on these parts will not materiallyaffect the efficiency of the system. Moreover, the entire control is inresponse to pressure variations in the evaporator, which is commonlydisposed Where the refrigerating effect is to be utilized (as forexample in the food chamber of a household electric refrigerator), sothat no separate thermostatic switch is required.

However, while I have described my invention in embodiments including areciprocating piston type of compressor, I do not Wish to be limited tothis or other details of the construction and arrangement heredisclosed, since many changes may obviously be made without departingeither from the spirit of my invention or from the appended claims.

With control mechanisms of thegeneral type of those shown in Fig. 2 andFig. 7, I also secure the added advantage that such a mechanism servesas a safety valve in case a derangement of the system permits thepressure in the condenser to become excessively high. In such a case,the high pressure would overbalance the electromagnetic pull on thevalve member of Fig. 2 and would likewise tend to move the lever of Fig.7, so as to open the valve and relieve the pressure by freely connectingthe condenser to the evaporator.

I claim as my invention.:

1. A refrigerating system including a compressor, condenser andevaporator successively and continuously connected in series with eachother, means for driving the compressor; and automatic control means forthrottling the connection between the condenser and the evaporator whenthe compressor is in operation, and for widely opening the saidconnection when the compressor is halted.

2. A refrigerating system including a compressor, condenser andevaporator successively and continuously connected in series with eachother, means for driving the compressor; a throttling valve disposed forcontrolling the connection between the condenser and the evaporator, andconjointly acting means responsive to the pressure in the evaporator forcontrolling the actuation of the com-- pressor and controlling thevalve.

3. A refrigerating system including a compressor, condenser andevaporator successively and continuously connected in series` with eachother; an electric motor driving the compressor; an electric circuitconnected to the motor; and means responsive to the vaporpressure in theevaporator for controlling the electric circuit and controlling theconnection between the condenser and the evaporator, the said meansbeing arranged for maintaining a seepage connection between thecondenser and the evaporator as long as the circuit to the motor isclosed.

4. A refrigerating system as per claim 3, in which the said meansinclude a switch in the electric circuit and an electromagnetic valvealso controlled by the switch and controlling the said connection.

5. A refrigerating system including a compressor, condenser andevaporator successively in series with each other; an electric motordriving the compressor; a valve casing interposed between the condenserand the evaporator; a valve member movable in the casing and arrangedtopermit a seepage of refrigerant from the condenser to the evaporatorwhen the valve member is in one position, and to permit a relativelyfree passage of refrigerant from the condenser to the evaporator whenthe movable valve member is in a second position electromagnetic meansarranged for holding the movable valve member in its first namedposition, and means responsive to the pressure in the evaporator forcontrolling both the operation of the motor and the electromagneticmeans.

6. An assembly of refrigerating system parts as per claim 5, in whichthe valve member is movable in one direction by the magnetic fiux in thecoil and in the opposite direction by the pressure of refrigerantflowing from the condenser to the evaporator.

7. For interposition between the condenser and evaporator of acompression refrigerating system, a valve casing; a valve memberslidable in the casing to control the passage of refrigerant through thecasing while continuously permitting refrigerant to flow from thecondenser to the evaporator, the valve member havinga portion ofmagnetizable material; a wire coil coaxial with and surrounding aportion of the valve member, an electric circuit connected to the coil,and means responsive to the pressure in the evaporator for controllingthe said circuit.

8. A refrigerating system including a compressor, condenser, valve andevaporator successively in series with each other, the valve including amember, movable between two positions in which it respectively affords amere seepage of refrigerant and a voluminous passage of refrigerantthrough it; means responsive to an increase of pressure in theevaporator above a predetermined minimum for holding the movable valvemember in its seepage affording position against the pressure ofrefrigerant in the condenser; and means responsive to a decrease ofpressure in the evaporator below the said minimum for `releasing thesaid holding of the valve member in its seepage affording position, thesaid member being then movable to its voluminous passage-aifordingposition by the pressure of refrigerant in the condenser.

9. Means for controlling the flow of refrigerant from the condenser totheY evaporator of a refrigerating system, comprising a valvel casinginterposed between the condenser and the evaporator, a valve membermovable in the casing from a first position in which it permits avoluminous passage of refrigerant to a second and eXtreme position inwhich it permits only a relatively restricted passage; connections fromthe casing to the condenser and the evaporator, the connections beingsuch that the flow refrigerant from thecondenser through the casing willtend to move the said valve member towards its said first position, andmeans responsive to a predetermined increase in the refrigerant vaporpressure in the evaporator for holding the said valve member in its saidfirst position.

10. Control means as per claim 9, in which the said pressure-responsivemeans are also arranged for moving the said valve member from its firstto its second named position when the vapor pressure in the evaporatordecreases to less than a predetermined minimum.

11. A compression refrigerating system including an intermittentlyactuated compressor having a compression chamber, an evaporator, and acondenser interposed between the compression chamber and the evaporatorand connected to both of the latter by continuously open connections;and cont-rol means including a single mechanism responsive to pressurechanges in the system for controlling the actuation of the compressorand for effecting a reduction of pressure in the compression chamber andthe condenser before each restarting of the compressor.

1Q. The combination with the compressor, condenser and the evaporator ofa compression refrigerating system, of a valve casing interposed betweenthe condenser and the evaporator, a valve member movable in the casingand arranged for continuously allowing refrigerant to flow from thecondenser to the evaporator, the valve member being arranged to permit amere seepage of refrigerant through the casing when the valve member isin one position, and permitting a full flow of refrigerant from thecondenser to the evaporator when in a second position; valve-holdingmeans responsive to the actuation of the compressor for moving the valveto and holding the valve in its said second position; the movable valvemember being movable from its said seepage permitting position towardits said second position by the pressure of liquid in the condenser whenthe said valve-holding means are inoperative.

Signed at Chicago 1928.

